Mining machine hydraulic control system and master safety valve therefor



Nov. 17, 1953 M. G. CARLSON 2,659,206 MINING MACHINE HYDRAULIC CONTROL SYSTEM AND MASTER SAFETY VALVE THEREFOR Filed April 18, 1951 Y INVENTOR.

ATTORNEY Patented Nov. 17, 1953 MINING MACHINE HYDRAULIC CONTROL SYSTEM AND MASTER THEREFOR SAFETY VALVE Melvin G. Carlson, Chicago, Ill., assignor to Goodman Manufacturing Company, Chicago, 111., a corporation of Illinois Application April 18, 1951, Serial No. 221,663

Claims. 1

This invention relates to mining machines and particularly to an improved hydraulic control system for a mining machine having a single master safety valve capable of protecting a plurality of use points against externally applied overloads.

In a mining and loading machine, which is one example where the present invention may be employed, a front boom carries a loading head which is swingable from side to side and up and down by fluid pressure operable cylinders. A rear boom is similarly movable. When the machine is trammed forward to thrust the loading head into a pile of shot coal, the reaction against the head tends to cause lifting or swinging movement which is resisted by back pressure in one or more of the operating cylinders. Likewise, the rear boom will sometimes be loaded externally as when it strikes a side or top of the room during tramming. To prevent the pressure caused by these externally applied loads becoming dangerously or destructively high, it has been customary practice in the mining machinery field to provide an individual pressure relief valve for each of the operating cylinder use points. Thus, for six cylinders or use points, for example, there would be six individual overload relief valves. This has been disadvantageous, not only due to the cost of the valves, but due to the space required in machines which must be made very compactly.

Accordingly, the present invention has for its primary object the provision of a hydraulic control system for a mining machine in which a single master safety valve replaces all the individual relief valves heretofore used. Briefly, l

the present invention employs a single main relief valve connected to all the use points and itself set corresponding to the lowest relief pressure required for any of the use points. Between each use point and the main relief valve are auxiliary combined check and relief valves, each set for a pressure, which, when added to the setting of the main valve, will be correct for the particular corresponding use point.

Other objects and advantages will be seen in the following description taken in connection with the drawing in which a mining and loading machine is shown and upon which is diagrammatically superimposed a hydraulic master safety control system in accordance with the present invention.

Referring now more particularly to the draw- .ing, the numeral 2! designates generally a mining and loading machine having a front boom 22 which is swingable from side to side by cylinder means 23 and 24, respectively, and a rear boom 26 which may be lifted by means of cylinders 21, 21. To simplify the present disclosure the cylinders 23 and 24 are indicated as single acting cylinders. The rear cylinders 21, 21 are likewise indicated as single acting, for the same reason.

It will be understood that a complete loading machine will normally have a number of other operating cylinders such, for instance, as those employed to swing the rear boom from side to side and to lift the front boom but, to simplify the disclosure, only the three sets of cylinders 23, 24 and 21 need be shown in order to illustrate the present invention.

To swing the loading head 22 to the right, about a vertical pivot point X, pressure is introduced from a pressure source P1 by a control valve 28 into a line 29 connecting with the head end of the cylinder 23. Similarly, to swing the head to the left, pressure is admitted from a pressure source P2 by valve 3| into a line 32 connecting with the head end of cylinder 24. Likewise, to lift the rear boom 26, about a horizontal axis Y-Y, pressure is admitted from a pressure source P3 through valve 33 into line 34 which is bifurcated at the machine and connects where it actually causes rupture of the line or other damage to the hydraulic circuit. Similarly, the lines 29 and 32 may be damaged by pressure rise if the machine is trammed forward to force the loading head 22 into a pile of coal at a time when the loading head is swung to one side or the other.

To eliminate the possibility of this dangerous or destructive over-pressure under such conditions it has been customary'in the past to provide each of the lines 29, 32 and 34 with an individual pressure relief valve.

In the present case the master safety valve means generally designated 36 comprises a single compact unit which takes the place of all the individual safety valves heretofore used. It comprises a casing 31 having an outlet port 38 and inlet ports 39, M, and 42 interconnected by a passageway 43 having a seat 44 and a ball valve element 46 pressed against the seat by a compression spring 41, the latter being held in place by a cap .48 threadedly engaged with the casing.

Each of the main relief valve inlets 39, 4|, and 42 has associated with it an auxiliary combined check and reliefvalve generally designated 49, 5|, and 52, respectively. Each auxiliary valve comprises a flanged bushing or casing 53 threadedly engaged with the main valve casing 31, as at 54 and being formed with a seat 56 on which is urged an auxiliary valve element 51 by means of a relatively small compression spring 58, the latter being seated, in turn, against a shoulder 59 formed in the main casing. Each of the bushings 53 is provided with an exterior threaded inlet port 5| with which the conduits 29a, 32a, and 3411 are respectively connected. The latter comprise pressure bypass means for the corresponding lines 29, 32, and 34, as will be. seen. The main casing outlet 38 is connected by means of a conduit 52 to a suitable overflow reservoir or tank T.

In operation, suppose for example that pressure should be relieved. from the cylinders 23. and 24 when an externally applied load causes it to rise to, say, 806 poundsper square inch; likewise, the pressure in cylinders 21. should be relieved when it rises to, say, (500- pounds per square inch. Under such a specific set of conditions the main relief valve spring 41' will be selected of such a size as to permit the main ball 46 to relieve at substantially 600 pounds per square inch. In this case the auxiliary spring 58 in the auxiliary valve 52 will be selected so as to exert a relatively light action against its ball, just enough to hold the ball against its seat.

The springs of the other two auxiliary valves 49 and 5| will be selected of sumcient strength to cause their corresponding ball valves 51 to be displaced by a. hydraulic pressure of substantially 200 pounds per square inch.

Thus, since the effect of the main and auxiliary relief valves will be additive, the front swing cylinders 23, 24 will be relieved at 800 pounds per square inch while, at the same time, through the same main casing 31, the rear lifting cylinders 21, 21 will be relieved at 600 pounds per square inch pressure.

As an additional safety feature for the particular hydraulic control system shown, each of lines 29 and 32 may be connected by a line H through a check valve 12 to the fluid reservoir or tank T. These check valves 12 would protect the lines 29 and 32 by preventing the formation of a vacuum therein in case a vacuum would have any harmful effect on components of the lines. For example, it will be seen that the particular cylinder and piston means 23 and 24, while each being shown as single acting, nevertheless operate together in somewhat the same fashion as a double acting cylinder and piston arrangement. That is when fluid is fed into the cylinder 23 the front boom 22 will be swung in a clockwise direction causing other fluid to be displaced from the cylinder means 24; and vice versa. Now, in the specific case illustrated, assume that an exteriorly applied overload thrusts the boom 22 in, say, a clockwise direction. Fluid will be displaced from the cylinder 24 through the relief valves 5| and 46 to the tank T as above described. This same movement of the head 22 will cause the cylinder.23 to attempt to draw in make-up. fluid which may be supplied by the tank T through the corresponding make-up line I I. This make-up fluid will move e dire t n 4 permitted by the check valve 12. As pointed out above, the check valves 12 are not essential but, where double acting cylinder means is employed, the auxiliary check valves 12 may be used to supply make-up fluid.

While one form in which the present invention may be. embodied, has been shown and described it will be understod that various modifications and variations thereof may be effected without departing from the spirit and scope of the invention. as defined by the appended claims.

I claim:

' 1. In a mining and loading machine having at least a pair of pressure operable use points thereon, means for directing pressure into each of said use: points, master safety valve means including relief valve means having a plurality of inlet ports, one of which is connected to each of said pressure operable use points, and check valve means associated with each of said inlet ports and effective. to prevent. backfiow from the relief valve means to the use points.

2. In. a mining and loading machine having a plurality of fluid pressure operable means for directing fluid under pressure. into each of said pressure operable means, master safety valve means including a main relief valve having a plurality of inlet ports, one of which is connected to each of said pressure operable means, and an auxiliary combined check. and relief valve associated with each of said inlet ports and effective to prevent backflow from the main relief valve to the pressure operable means, each of said auxiliary valves having a pressure-relieving funotion which is additive with that of the main relief valve to thereby relieve each of said pressure operable means at a pressure determined by the summation of the setting of the main relief valve and the corresponding auxiliary valve.

3. In a mining and loading machine having a plurality of pressure operable use points, and means for directing pressure into each of said use points, master safety valve means including a main relief valve comprising a casing having inlet and outlet ports with a seated passageway therebetween controlled by a spring loaded valve element, an auxiliary combined check and relief valve connected between each of said use points and one of said inlet ports and effective to prevent backiiow from the main valve to the corresponding use point, each of said auxiliary valves comprising a casing having a seated fluid passageway controlled by a spring loaded auxiliary valve element, whereby the pressure at each use point will be relieved at a value dependent on the summation of the setting of the main valve spring and the setting of the corresponding auxiliary valve spring.

4. In a mining and loading machine having a plurality of pressure operable use points, and means for directing pressure into each of said use points, master safety valve means including a main relief valve comprising a casing having inlet and outlet ports with a seated passageway therebetween controlled by a spring loaded valve element, an auxiliary check valve connected between each of said use points and one of said inlet ports and effective to prevent backflow from the main valve to the corresponding use point, each of said check valves comprising a casing having a seated fluid passageway controlled by a spring loaded valve element, whereby the pressure in all of said use points Will be relieved through said main valve at a value corresponding to the setting of the spring in the main valve.

5. In a machine having a hydraulic operating and control system including a plurality of pressure operable use points and means for directing pressure into each of said use points, master safety valve means including a main relief valve comprising a casing having inlet and outlet ports with a seated passageway therebetween controlled by a spring loaded valve element, an auxiliary combined check and relief valve connected between each of said use points and one of said inlet ports and efiective to prevent backflow from the main valve to the corresponding use point, each of said auxiliary combined check and 15 238L108 relief valves comprising a member having a seated fluid passageway controlled by an auxiliary spring loaded valve element, whereby the pressure at each use point will be relieved at a value dependent on the summation of the setting of the main valve spring and the setting of the corresponding auxiliary valve spring.

MELVIN G. CARLSON.

References Cited in the file of this patent UNITED STATES PATENTS Name Date Clarkson et al Jan. 11, 1944 Cartlidge Aug. 7, 1945 Number 

